More Support for Human Role in Chinese Quake

ScienceNOW Daily News ^ | 6 November 2009 | Richard A. Kerr

[neverdem]

When the Wenchuan earthquake killed some 80,000 people in southwest China in May of last year, suspicion immediately fell on the reservoir behind the nearby Zipingpu Dam. Seismologists knew that several hundred million tons of water had filled the reservoir in the preceding few years and that either the water itself or its weight might have weakened a nearby fault and unleashed the quake. A new analysis finds that both scenarios are plausible, but further insight will require the cooperation of the Chinese government.

Last December, an American researcher was the first to prominently report (Science, 16 January, p. 322) that the Wenchuan quake may have been triggered by human activity. That study focused on the idea that the sheer weight of the water in the reservoir may have weakened the adjacent Beichuan fault, either by counteracting the stress that was strengthening the fault by squeezing it together or by adding to the stress tending to rupture the fault.

The new analysis finds support for the added-weight hypothesis and also for the idea that the water itself might have seeped kilometers downward into the fault, where quakes get started. Once there, it could have pressurized the water, pushing the fault apart and weakening it. When hydrogeologist Shemin Ge of the University of Colorado, Boulder, and her colleagues put both the water's weight and plausible penetration of the water into their calculations, the amount and direction of stress change on the fault came out to be about what large quakes create when they trigger failure in nearby faults. "We thus suggest," the authors write in their 28 October Geophysical Research Letters paper, "that the Zipingpu Reservoir potentially hastened the occurrence of the Wenchuan earthquake by tens to hundreds of years."

That "is plausible," says seismologist Ross Stein of the U.S. Geological Survey in Menlo Park, California. But the case isn't yet closed, Stein says. The study "shows a possibility, not a probability."

To make stronger statements, more observations would have to be incorporated into analyses, says Stein. Many such data sets may exist, he says, but the Chinese government has kept them off-limits for most researchers. Meanwhile, he says, China and India continue to build large dams in settings just like Zipingpu's, he notes. If they proceed, such projects demand close monitoring long before the water goes in.

[Right Wing Assault]

It is thought that water can act as a lubricant between rocks to let them slip sooner than they usually would. Injecting water deep underground has been suspected as a factor in other quakes.

[Hardastarboard]

Man caused earthquakes. What will the Communist ruling elite think of next?

[neverdem]

Signature of antimatter detected in lightning

Experts Criticize Nanoparticle Study

Longevity Tied to Genes That Preserve Tips of Chromosomes

FReepmail me if you want on or off my health and science ping list.

[xJones]

The mother of all damns that have never have been built is the Three Gorges Dam in China. It's right on a major fault zone and damming up the Yangtze River.

[xJones]

that have never have been built

Sorry, replace that with "that should never have been built." '

[happygrl]

One of the few large earthquakes in Central Africa was right after Kariba Dam on the Zambezi River, was filled.

There was a huge reservoir built in Riverside County, CA a decade ago near the San Jacinto fault. Among the assumptions was that it might trigger a mid-size quake when filled.

So far, so good, but it might still happen.

[neverdem]

The mother of all damns that have never have been built is the Three Gorges Dam in China. It's right on a major fault zone and damming up the Yangtze River.

That could finally tempt the mandate of heaven.

[Ramius]

On the Three Gorges dam... I understand that there are some serious concerns about it, from the quality of the engineering to the quality of the materials. If that sucker breaks it’s going to kill an epic number of people downstream. It would be staggering.

[SunkenCiv]

Seismologists knew that several hundred million tons of water had filled the reservoir in the preceding few years and that either the water itself or its weight might have weakened a nearby fault and unleashed the quake.

Weird that this human activity (building a reservoir) caused a quake, considering that the reservoir didn't exist when all the other deadly quakes hit the same region throughout recorded Chinese history. :') Thanks neverdem.

· join · view topics · view or post blog · bookmark · post new topic · subscribe ·